The present invention relates to high temperature corrosion resistant hard surfacing alloys which are of extremely high hardness. More particularly, the present invention relates to hard surfacing alloys which contain tungsten carbide, chromium carbide and bi-metallic tungsten chromium carbide precipitates which are precipitated in the alloy and are thus bound in the hard surfacing alloy. Alloys of the present invention produce superior surfaces for improved wear in high temperature high corrosive environments such as glass mould plungers and the like.
Plungers used in glass moulding are exposed to some of the most extreme and corrosive environments which are found in modern industry. These plungers are subjected to hundreds of thousands of high impact high temperature plunging operations in the glass moulding industry. In the past, these plungers have been a source of down time in that they are subject to rapid wear. Also, plungers used in the glass mould industry must have surfaces be of very low porosity to provide the proper surface in the final finished glass piece. Thus, improper wearing of plunger surfaces mandates repair or replacement. Prior alloys used for surfacing of glass mould plungers have demonstrated "hot wiping" of the alloys from the glass plunger surface. This condition reduced longevity in that the surface alloy was worn away creating out of specification conditions requiring replacement and/or repair.
It has been known that if hard surfacing alloys could be achieved which have high Rockwell C hardnesses of greater than 50, such an alloy would greatly increase longevity of these plungers. However, such alloys have not been readily available in the prior art.
Because of such high Rockwell C hardness requirements it has been generally recognized that materials containing carbides such as tungsten carbides and the like would be advantageous in such alloys.
In other applications, high hardness alloys have been successfully utilized using sintered cobalt structures employing tungsten carbide particles which are encapsulated therein. These cobalt sintered structures rely on the encapsulation of tungsten carbide particles in the alloy to produce high hardness type alloys in the ranges necessary for glass mould plungers. Such alloys are known and have been used in other applications, however, when these alloys are used in glass plunger applications it was found that the final plunger produced by such an alloy was not suitable for a glass plunger application due to the porosity of the alloy produced. Such porosity is undesirable as stated above. Additionally, because of the extreme working conditions in glass plunger applications extraordinary quantities of tungsten carbides would need to be utilized. The sintered type structures have not been found to readily accommodate such high quantities of tungsten carbides.
Sintered structures also are prone to loss of the critical tungsten carbide particles under use, apparently due to the relatively "loose" encapsulation of tungsten carbides in the structure. Thus, as these structures wear the tungsten carbide particles tend to dislodge from the structure reducing the hardness of the structure.
Thus, it has been a goal in the art to provide a high hardness surfacing alloy which contains high quantities of tungsten carbide particles and the like and which has low porosity characteristics.